Maximally-localized Wannier functions for entangled energy bands

We present a method for obtaining well-localized Wannier-like functions (WFs) for energy bands that are attached to or mixed with other bands. The present scheme removes the limitation of the usual maximally-localized WFs method (N. Marzari and D. Vanderbilt, Phys. Rev. B 56, 12847 (1997)) that the bands of interest should form an isolated group, separated by gaps from higher and lower bands everywhere in the Brillouin zone. An energy window encompassing N bands of interest is specified by the user, and the algorithm then proceeds to disentangle these from the remaining bands inside the window by filtering out an optimally connected N-dimensional subspace. This is achieved by minimizing a functional that measures the subspace dispersion across the Brillouin zone. The maximally-localized WFs for the optimal subspace are then obtained via the algorithm of Marzari and Vanderbilt. The method, which functions as a postprocessing step using the output of conventional electronic-structure codes, is applied to the s and d bands of copper, and to the valence and low-lying conduction bands of silicon. For the low-lying nearly-free-electron bands of copper we find WFs which are centered at the tetrahedral interstitial sites, suggesting an alternative tight-binding parametrization.Comment: 13 pages, with 9 postscript figures embedded. Uses REVTEX and epsf macro

Maximally-localized generalized Wannier functions for composite energy bands

We discuss a method for determining the optimally-localized set of generalized Wannier functions associated with a set of Bloch bands in a crystalline solid. By ``generalized Wannier functions'' we mean a set of localized orthonormal orbitals spanning the same space as the specified set of Bloch bands. Although we minimize a functional that represents the total spread sum_n [ _n - _n^2 ] of the Wannier functions in real space, our method proceeds directly from the Bloch functions as represented on a mesh of k-points, and carries out the minimization in a space of unitary matrices U_mn^k describing the rotation among the Bloch bands at each k-point. The method is thus suitable for use in connection with conventional electronic-structure codes. The procedure also returns the total electric polarization as well as the location of each Wannier center. Sample results for Si, GaAs, molecular C2H4, and LiCl will be presented.Comment: 22 pages, two-column style with 4 postscript figures embedded. Uses REVTEX and epsf macros. Also available at http://www.physics.rutgers.edu/~dhv/preprints/index.html#nm_wan

Fatal toxic epidermal necrolysis in autoimmune polyglandular syndrome type I

Autoimmune polyglandular syndrome Type I (APS I) is a disorder defined by the presence of at least two of the following diseases: Addison's disease, hypoparathyroidism, and chronic mucocutaneous candidiasis. We present the case of a 45-yr-old woman, affected by APS I, in chronic treatment with betamethasone. She was referred to a Division of General Medicine for jaundice, ascites and peripheral edema attributed to worsening of pre-existing autoimmune chronic hepatitis. During hospitalization, the following drugs were given: Amoxicillin/Clavulanic acid and Levofloxacin for bronchopneumonia, Furosemide and Canreonate for renal impairment, Pantoprazole for gastric protection, and Itraconazole for oral candidiasis. After about a month, she developed widespread, sheet-like, epidermal detachment, with painful lesions of the conjunctiva, lips and mouth. Toxic epidermal necrolysis (TEN) was diagnosed, and the patient was transferred to a Burn Center, where she died 10 days after the first onset of cutaneous rash. Autoptic and histopathological findings (epidermal necrosis and detachment, lymphomonocytic infiltration of the dermis) confirmed the clinical diagnosis. TEN is a usually drug-induced cutaneous inflammatory disorder characterized by extensive epidermal detachment and frequent mucosal involvement. It has also been associated with immuno-mediated disorders (HIV infection, graft-vs-host disease, systemic lupus erythematosus, mixed essential cryoglobulinemia), in keeping with immuno-mediated pathogenesis. We present, to our knowledge, the first report of TEN in a patient with APS I, and suggest that some pathogenetic mechanisms of APS I are shared with TEN. We stress how such a disease can occur in an autoimmune syndrome, even during corticosteroid treatment